br>I purchased a eurorack STG Mankato filter used and I think it has a problem.

Initially, the filter seemed to work. I took a saw wave coming out of my oscillator into the Mankato. The filter cutoff seemed to work as it should. However, something was clearly wrong when I tried to engage the filter resonance. The resonance seemed to only worked over an octave or so, from 1 to 2 o'clock on the dial. Above and below that, the resonant sine wave just disappeared. No high frequencies, no low frequencies. I was looking at it on a scope, so it wasn't just me. I pulled the patch cable from my oscillator and turned the resonance up full. Again, absolutely no output past 2 o'clock (high frequencies >8k or so), nor any mid to low frequencies. Below 1 o'clock, the sine wave disappeared again.

The Mankato has behaved this way, with the resonance issue, for most of the time I have had it (maybe a month). However, there have been a couple of time that I have powered it up and the resonance seemed to work properly, but the filter then added a crazy amount of noise to the output, about as loud as the incoming signal. It didn't sound like clipping, it was more like pink noise had been added to my input signal. On the scope, the output voltage range also shifted upward, going from about +1v to +10v. That has only happened a couple times. When I have unplugged it and powered it back up, it has gone right back to the resonance error state.

I tried the Mankato with two different power systems, both brand new: a 4ms Row Power 30, and a Synthrotek Super Power Blue. The power coming from the wall was correctly wired and grounded (I checked).

I'm assuming that something is really wrong and requires repair. I emailed STG Soundlabs about a week ago, but haven't heard anything. I know it's a small operation, but it's hard to be patient when your email seems to just disappear out into the void. For all I know, my email got mulched by their spam filter. Any experiences with repairs done by STG? Should I be going about this some other way?

Thanks for any advice.
br> br>

br>Just me

br>He is out of town at a synth gathering right now. Try another email and see if he responds. It may have gotten lost in the hubub. br> br>

br>suitandtieguy

br>yes i was at Sweetwater's Gearfest this weekend, highly distracted as usual over the past week, i'm sorry.

the guy that sold you the Mankato did contact me and I assured him I would deal with it and it was highly unlikely anything he did while he owned it caused this, but this is kind of weird and might require a return for examination.